Submitted to ITU-R WP5a by the ARRL;
"To maintain the relevance and functionality of the International Morse code by adding a character corresponding to the printed character “#”, variously known as a thorpe, octothorpe, pound sign, or hash."
Cutting edge, these guys are!
No date, no link reference. I couldn't find any reference in the current agenda items for WRC-15.
But, in today's world, the "#" should have a character reference in the International Morse Code,
http://morsecode.scphillips.com/morse.html